Radio resource management (RRM) is one of the most critical functions in a wireless network. It determines the overall utilization and efficiency of the radio network as well as the quality of service (QoS) experienced by the mobile users. Two main functions of RRM are the call admission control (CAC) and the dynamic bandwidth allocation (DBA) procedures.
CDMA systems are interference limited and their capacity is largely determined by the carried traffic characteristics and the radio resources management mechanisms employed. This is even more critical for integrated networks where both voice and data traffic are serviced. The overall traffic mixture have a wider degree in variability, compared to voice networks, and thus the interference environment is more dynamic. The goal of a successful RRM policy is to optimize the system capacity without adversely affecting the quality of service for voice or data calls.
Data traffic, especially for Internet applications, is typically characterized as being bursty that is there are bursts of traffic with idle time therebetween. During bursts, the network, ideally, should allocate the required resources to transmit the information at the granted bit rate. However, since the interference level varies as the carried load in the overall network varies, it is not possible to allocate the required resources all of the time. Current systems employ static resource allocation schemes that do not provide optimal capacity or throughput for mobile users. These schemes are not able to respond to the variation in the traffic demand and interference level.
Initial deployments of CDMA integrated networks include legacy RRM routines that are usually static in nature and do not account for the network dynamics, in terms of interference level and bandwidth requirement. Static RRM routines and functions lead to poor utilization of the radio spectrum and do not maximize the network throughput.
The call admission control procedure is especially critical for integrated networks. A conventional method used in the art is to divide the resources such as RF power and codes between voice and data calls in a way that achieves an acceptable performance for both services under general operating conditions. Using this simple method, the designer would specify the fraction of resources that can be used for voice traffic. Assuming the network serves only voice and data, this automatically specifies the fraction of resources that can be used for data.
One way to circumvent effects of traffic variation is to employ a more intelligent partitioning scheme. A known method used in the art is to allow the resources to be shared among different types of traffic with/without assured guaranteed share of resources to any type of traffic. It is obvious that such scheme provides a level of dynamic sharing of resources; yet, the network has no preference to either type of traffic and the amount of resources occupied by one type of traffic compared to that occupied by the other is totally dependent on the arrival process of the traffic. Hence, if at some period of the day, data calls arrive at a much higher rate compared to arrivals of voice calls, it is possible that network resources will be totally supporting data calls with none allocated or reserved for voice. This may not be desirable by the operator, especially if voice service is considered to be the primary service. Of course, the opposite scenario where voice calls occupying all the network resources and depriving data users based on the traffic condition (the ratio of voice calls arrival rate to data calls arrival rate) at one particular period of the day may also be not desirable for an operator that would likes to balance data and voice usages.
The operator may design these partitions, referred to herein as maximum fractions of resource usage, for each type of traffic for a particular mix and intensity of call arrivals, but these partitions will cease to be appropriate when the traffic mix and intensity change either from one time of the day to another or from one day to the next.
When a total sharing solution is implemented, i.e. no partitioning or any type of traffic is allowed to use 100% of the resource, the network has no preference to either type of traffic. The amount of resources occupied by one type of traffic compared to that occupied by the other is totally dependent on the arrival process of the traffic. Although, the total sharing case, may appear to allow the maximum allocation flexibility it does not guarantee a specific grade of service for the carried traffic and hence may not be favored by the operator. The arrival process of traffic, which is beyond the control of the operator, dictates the provisioning of resources in the network and the grade of service experienced by the end user.
The flexibility of the wireless CDMA platform makes it very suitable for integrated services networks. It allows users of diverse traffic to be integrated. However, the burstiness of data traffic and the heterogeneous nature of data users make the assignment of data transmission rates and the granted burst duration very critical. An important question that needs to be answered is how to share the scarce network resources amongst users such that network performance is optimal?
The current art serves a data burst on a best effort basis. Typically, a data burst request is initiated whenever there is a need regardless of the requirements of other competing users. If resources are not sufficient to support the request even after downgrading its original requirements, the request shall be deferred randomly to have another chance later. This kind of best effort service does not provide any quality of service guarantee nor optimizes resources utilization.
As mentioned before, the determination of data burst rate and burst length in wide-band CDMA networks greatly influences their overall performance since data bursts are usually associated with high power and high bit rate transmissions. These have considerable effects on other ongoing activities in a CDMA environment.
Consequently, there is a need for new radio resource management schemes to accommodate the different requirements of data traffic when compared to voice. This would allow the efficient deployment of data services over what used to be mainly voice-oriented infrastructure.